The little girl used pertinacity to get the ice cream.

The proprietor had pertinacity and persistence and would relentlessly push his product.

Even though they face many failures, doctors still search for cures with great pertinacity.

bullheadedness, determination, doggedness, hardheadedness, mulishness, obstinance, obstinateness, pertinaciousness, pertinacity, perversity, pigheadedness, purpose, reluctance, tenaciousness, tenacity, willfulness

diligence, stubbornness, courage, determination, doggedness, firmness, grit, inflexibility, perseverance, persistence, pertinacity, resoluteness, resolve, staunchness, steadfastness, strength of purpose,